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Experiment 9
Light Phenomena
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Refraction of Light
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The Index of Refraction
sm1000.3 8cLight travels through a vacuum at a speed
Light travels through materials at a speed less than its speed
in a vacuum.
DEFINITION OF THE INDEX OF REFRACTION The index of refraction of
a material is the ratio of the speed of light in a vacuum to the
speed of light in the material:
v
cn
material in thelight of Speed
in vacuumlight of Speed
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The Index of Refraction
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Snells Law and the Refraction of Light
SNELLS LAW OF REFRACTION When light travels from a material with
one index of refraction to a material with a different index of
refraction, the angle of incidence is related to the angle of
refraction by
2211 sinsin nn
SNELLS LAW
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Snells Law and the Refraction of Light
1
2
n
ndd
Apparent depth, observer directly above object
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Snells Law and the Refraction of Light
THE DISPLACEMENT OF LIGHT BY A SLAB OF MATERIAL
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The Dispersion of Light: Prisms and Rainbows
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Lenses
Lenses refract light in such a way that an image of the light
source is formed.
With a converging lens, paraxial rays that are parallel to the
principal axis converge to the focal point.
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Lenses
With a diverging lens, paraxial rays that are parallel to the
principal axis appear to originate from the focal point.
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Lenses
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Reflection of Light
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The Reflection of Light
LAW OF REFLECTION The incident ray, the reflected ray, and the
normal to the surface all lie in the same plane, and the angle of
incidence equals the angle of reflection.
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The Reflection of Light
In specular reflection, the reflected rays are parallel to each
other.
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The Formation of Images by a Plane Mirror
The persons right hand becomes the images left hand. The image
has three properties: 1. It is upright. 2. It is the same size as
you are. 3. The image is as far behind the mirror are you are in
front of it.
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Activity 1: Refraction A. Index of Refraction of Glass
Incident angle
Refracted angle
10
15
20
25
30
35
40
sin i
sin r
r
in
sin
sin2
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Activity 1: Refraction B. Refraction through Parallel Plate
Angle of Incidence
Angle of Refraction
Emergent Angle
% Difference between incident and emergent angle
Measured lateral displacement
Computed or theoretical lateral displacement
% Difference
r
ii
n
ntd
cos
cos1sin
2
1
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Activity 1: Refraction C. Refraction through Spherical
Surfaces
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Activity 2: Reflection
Angle of Incidence Angle of Reflection % Difference
ri
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Activity 3: Inverse Square Law for Light Intensity
d (cm) I (lux)
10 cm
20 cm
30 cm
40 cm
50 cm
60 cm
I (lux)
d (cm)
